“I will decree upon you panic, disease and fever, making your eyes weaken and your souls suffer; you shall sow your seed in vain, for your enemies shall eat it; your strength shall be spent in vain, and I will punish you seven times for your sins…” (Lev.26).
True, the rewards for obedience to God will be worth having, but why must all this be spelt out in such detail? We all know what to do and what not to do. We are grown up enough to be aware of our duty. Are rewards and punishments really necessary?
In general principle the answer has to be no. The right thing should be done lishmah, for its own sake, not for the sake of a reward or to avoid punishment. The point is made in Pirkei Avot (ch. 1) by Antignos of Socho who told his disciples not to be like servants who minister to their master on condition of receiving a reward.
Since not everyone is ready to serve God on the highest level, obedience is spurred on by the promise of reward or the threat of punishment.
Some are surprised that the rewards listed in the Torah are all material and this-worldly.
Ibn Ezra believes that spiritual rewards might not help the majority of people, who understand only physical things. Nachmanides argues (commentary on Deut. 11:13) that since it is axiomatic that God will give spiritual rewards, only the material aspects need to be stated.
Nonetheless, human experience is that material rewards do not always come. The wicked often prosper and the righteous suffer. Some say that it is in the here-and-now that things are not always fair but all will be put right in the World to Come.
Joseph Albo (Ikkarim 4:39) offers the suggestion that it is the nation as a whole which receives the earthly reward or punishment, but not necessarily the individual.